1. Field of Invention
The present invention relates to a projection optical system and an exposure apparatus provided with a projection optical system. In particular, the present invention relates to a suitable catadioptric type projection optical system in an exposure apparatus used when fabricating microdevices such as semiconductors or the like in a photolithographic process.
2. Description of Related Art
In recent years, the miniaturization in semiconductor device fabrication and. semiconductor chip packaging fabrication is increasing, and a projection optical system with a higher resolution is required for a photolithographic exposure device. To satisfy this resolution requirement, the wavelength of the exposure light is shortened, and the NA (the numerical aperture of a projection optical system) is increased. However, when the wavelength of the exposure light is shortened, the types of optical glass that are able to be used are limited due to light absorption.
For example, when using light in a vacuum ultraviolet region with a wavelength of 200 nm or less, an F2 laser (wavelength 157 nm) in particular, as the exposure light, a fluoride crystal such as calcium fluoride (fluorite: CaF2) and barium fluoride (BaF2) must be used as a radiation transmissive optical material in the projection optical system. In reality, a design that forms a projection optical system with only fluorite is assumed in an exposure apparatus using an F2 laser. Fluorite is a cubic system that was thought to be optically isotropic and to have substantially no birefringence. Further, in prior visible light experiments, only low birefringence (random occurrences caused by internal stress) has been observed in fluorite.
However, at a symposium (2nd International Symposium on 157 nm Lithography) concerning lithography held on May 15, 2001, John H. Burnett et al. of the U.S. NIST announced that he confirmed both in theory and by experiment that fluorite has an intrinsic birefringence.
According to this presentation, fluorite birefringence is nearly zero in the crystal axis direction [111] and the equivalent axes [xe2x88x92111], [1xe2x88x9211] and [11xe2x88x921], and in the crystal axis [100] and equivalent axes [010] and [001], but other directions have a value which is not substantially zero. In particular, the six crystal axis directions [110], [xe2x88x92110], [101], [xe2x88x92101], [001] and [01xe2x88x921] have a maximum birefringence of 6.5 nm/cm for a wavelength of 157 nm and 3.6 nm/cm for a wavelength of 193 nm. These values of birefringence are substantially greater than 1 nm/cm, the permissible value of random birefringence. However, for the portion that is not random the effect of birefringence may accumulate through multiple lenses.
Previously, the birefringence of fluorite was not considered in designing a projection optical system, so from the perspective of working ease, the crystal axis [111] and the optical axis are generally aligned. In such a case, in a projection optical system, the NA (numerical aperture) is comparatively large, so the crystal performance may deteriorate due to the effect of birefringence because the light ray that is somewhat tilted from the crystal axis [111] also passes through the lens.
However, Burnett et al. revealed in the presentation mentioned above, a method of compensating for the effect of birefringence by aligning the optical axis of a pair of fluorite lenses with the crystal axis [111] and rotating a pair of fluorite crystals 60xc2x0 relatively with the optical axis at the center. It is possible to alleviate the effect of birefringence with this method, but the effect of the compensation is not sufficient because the effect of birefringence is not actively compensated for due to the effect of birefringence in the opposite direction.
Also, when using F2 laser light (157 nm wavelength) as an exposure light, the outgas from the photoresist caused by exposure is unavoidable. Therefore, unless extraordinary steps are taken, it is impossible to avoid a contamination of the lenses caused by outgas in a conventional projection optical system having a large numerical aperture.
The present invention addresses the above-described problems. One object of the present invention is to provide a projection optical system having excellent optical performance that is substantially not affected by birefringence even when using optical materials with intrinsic birefringence such as fluorite, for example, and to provide an exposure apparatus having the projection optical system. A further object of the present invention is to provide a projection optical system capable of effectively avoiding contamination of the lenses caused by outgas from the photoresist, and to provide an exposure apparatus as part of the projection optical system.
In order to address the above-described problems, a first aspect of the present invention provides a projection optical system capable of forming a reduced image of a first surface onto a second surface, and includes a plurality of lenses and at least one concave reflective mirror, wherein the projection optical system, when used in an exposure apparatus to scan expose the first surface onto the second surface while moving the first surface and the second surface along a scanning direction, forms a slit-shaped or arc-shaped exposure area at the second surface when not scanning; and satisfies the conditional expression
0.5 less than (Dwxc2x7Nw)/Ew less than 1.4xe2x80x83xe2x80x83(1)
where Dn is a working distance of the second surface side, Nw is a numerical aperture of the second surface side, and Ew is a length in the direction orthogonal to the scanning direction in the slit-shaped or arc-shaped exposure area. It should be noted that a slit shape in the present invention refers to a shape extending in a direction across a scanning direction, for example, a rectangular, trapezoidal or hexagonal shape extending in a direction across a scanning direction.
According to a preferred embodiment of the first aspect of the invention, a projection optical system has a slit-shaped or arc-shaped exposure area that does not intersect the optical axis of the projection optical system. The projection optical system is provided with a refractive type first optical imaging system to form a first intermediate image of a first surface; a second optical imaging system, having at least one negative lens and a concave reflective mirror, to form the first intermediate image into a second intermediate image of nearly the same magnification near the first intermediate image forming position based on the light beam from the first intermediate image; a refractive type third optical imaging system to form a reduced image of the second intermediate image onto a second surface based on the light beam from the second intermediate image; a first optical path folding mirror arranged in the optical path between the first optical imaging system and the second optical imaging system; and a second optical path folding mirror arranged in the optical path between the second optical imaging system and the third optical imaging system. In this case, the effective area of the first optical path folding mirror and the effective area of the second optical path folding mirror preferably have a reflective surface formed across the whole of the planar surface. It is preferable that the effective area of the first optical path folding mirror and the effective area of the second optical path folding mirror not have a spatial overlap, and be arranged such that the whole light beam from the first surface is guided to the second surface.
Further, according to a preferred embodiment of the first aspect of the invention, all lenses comprising the first optical imaging system and the third optical imaging system are arranged along a single straight line along the optical axis. Furthermore, in the first aspect of the present invention, the projection optical system is preferably provided with a catadioptric type imaging system including a concave reflective mirror arranged in the optical path, between the first surface and the second surface; a refractive type imaging system arranged in the optical path between the catadioptric type optical imaging system and the second surface; a first optical path folding mirror arranged in the optical path between the first surface and the catadioptric type optical imaging system; and a second optical path folding mirror placed in the optical path arranged in the optical path between the catadioptric type optical imaging system and the refractive type optical imaging system.
A second aspect of the present invention provides a projection optical system including a plurality of lenses, a concave reflective mirror and a negative lens arranged in proximity to the concave reflective mirror, and is capable of forming a reduced image of a first surface at a second surface. The projection optical system, when used in an exposure apparatus to scan expose the first surface at the second surface while moving the first surface and the second surface along a scanning direction, forms a slit-shaped or arc-shaped exposure area at the second surface when not scanning; and the numerical aperture of the second surface side is 0.82 or more.
In one example, the concave reflective mirror and the negative lens are arranged along an optical axis in a direction substantially different from the direction of gravity, and the following conditional expression is satisfied:
1.0 less than S/|R| less than 1.8xe2x80x83xe2x80x83(2)
wherein S is the clear aperture (diameter) of the concave reflective mirror and R is the radius of curvature of the concave reflective mirror. Further, in the second aspect of the present invention, the projection optical system is preferably provided with a catadioptric type imaging system including a concave reflective mirror arranged in the optical path between the first surface and the second surface; a refractive type imaging system arranged in the optical path between the catadioptric type optical imaging system and the second surface; a first optical path folding mirror arranged in the optical path between the first surface and the catadioptric type optical imaging system; and a second optical path folding mirror placed in the optical path arranged in the optical path between the catadioptric type optical imaging system and the refractive type optical imaging system.
A third aspect of the present invention provides a projection optical system capable of forming a reduced image of a first surface at a second surface, wherein the projection optical system is arranged in an optical path between a pupil position of the second surface side and the second surface, has a substantially transmissive characteristic for light with a wavelength of 200 nm or less, and is provided with at least one radiation transmissive member formed such that a crystal axis [100] or an optically equivalent crystal axis to the crystal axis [100] nearly aligns with the optical axis.
A fourth aspect of the present invention provides a projection optical system capable of forming a reduced image of a first surface at a second surface, wherein at least one radiation transmissive member of the radiation transmissive members exceeding a maximum angle of the transmitting light ray of 20 degrees to the optical axis has substantially transmissive characteristics for light with a wavelength of 200 nm or less, and is formed such that a crystal axis [100] or an optically equivalent crystal axis to the crystal axis [100] nearly aligns with the optical axis.
A fifth aspect of the present invention provides a projection optical system capable of forming a reduced image of a first surface at a second surface, wherein the projection optical system is provided with: a first group of transmissive members formed such that the crystal axis [100] or an optically equivalent crystal axis to the crystal axis [100] nearly aligns with the optical axis, and has substantially transmissive characteristics for light with a wavelength of 200 nm or less; a second group of transmissive members formed such that the crystal axis [100] or an optically equivalent crystal axis to the crystal axis [100] nearly aligns with the optical axis, and has substantially transmissive characteristics for light with a wavelength of 200 nm or less; wherein the first group of transmissive members and the second group of transmissive members have a positional relationship relatively rotated about 45 degrees around the optical axis; and both the first group of transmissive members and the second group of transmissive members are arranged in the optical path between the pupil position on the second surface side and the second surface.
A sixth aspect of the present invention provides a projection optical system capable of forming a reduced image of a first surface at a second surface, wherein the projection optical system is provided with: a first group of radiation transmissive members formed such that the crystal axis [100] or an optically equivalent crystal axis to the crystal axis [100] nearly aligns with the optical axis, and has substantially transmissive characteristics for light with a wavelength of 200 nm or less; a second group of radiation transmissive members formed such that the crystal axis [100] or an optically equivalent crystal axis to the crystal axis [100] nearly aligns with the optical axis, and has substantially transmissive characteristics for light with a wavelength of 200 nm or less; wherein the first group of radiation transmissive members and the second group of radiation transmissive members have a positional relationship relatively rotated about 45 degrees around the optical axis; and in both the first group of radiation transmissive members and the second group of radiation transmissive members, the maximum angle of the transmitting light ray to the optical axis is greater than 20 degrees.
It should be noted that in the fifth and sixth aspects of the present invention, to relatively rotate the first group of lens elements and the second group of lens elements about 45 degrees around the optical axis means that the relative angle of the predetermined crystal axes (for example, crystal axes [010], [001], [01xe2x88x921], or [011]) which are facing in different directions from the optical axis in the first group of lens elements and the second group of lens elements is about 45 degrees around the optical axis. Furthermore, when the crystal axis [100] serves as the optical axis, rotational asymmetry stemming from the effect of birefringence with the optical axis at the center appears at a 90 degree period, so in the fifth and sixth aspects of the invention, to relatively rotate only about 45 degrees around the optical axis means the same as relatively rotating only about 45 degrees+(n*90 degrees) around the optical axis (where n is a whole number).
According to preferred embodiments of the fifth and sixth aspects of the invention, at least one of the first group of radiation transmissive members and the second group of radiation transmissive members has at least one aspherical surface. Further, it is preferable that the conditional expression |T1xe2x88x92T2|/TA less than 0.025 is satisfied, wherein T1 is the total thickness (center thickness) of the first group of radiation transmissive members along the optical axis, T2 is the total thickness of the second group of radiation transmissive members along the optical axis, and TA is the total thickness along the optical axis of all the radiation transmissive members comprising the projection optical system. Furthermore, the first group of radiation transmissive members and the second group of radiation transmissive members are preferably formed as one optical member by optical contact or by adhesion.
A seventh aspect of the present invention provides a projection optical system which includes a plurality of lenses, a concave reflective mirror and a negative lens arranged in proximity to the concave reflective mirror, and which is capable of forming a reduced image of a first surface at a second surface, wherein the negative lens has substantially transmissive characteristics for light with a wavelength of 200 nm or less, and is formed such that the crystal axis [100] or an optically equivalent crystal axis to the crystal axis [100] nearly aligns with the optical axis.
An eighth aspect of the present invention provides a projection optical system including a plurality of lenses, a concave reflective mirror, and a first negative lens and a second negative lens arranged in proximity to the concave reflective mirror, and capable of forming a reduced image of a first surface at a second surface, wherein: a) the first negative lens is formed such that the crystal axis [100] or an optically equivalent crystal axis to the crystal axis [100] nearly aligns with the optical axis, and has substantially transmissive characteristics for light with a wavelength of 200 nm or less; b) the second negative lens is formed such that the crystal axis [100] or an optically equivalent crystal axis to the crystal axis [100] nearly aligns with the optical axis, and has substantially transmissive characteristics for light with a wavelength of 200 nm or less; and c) the first negative lens and second negative lens have a positional relationship relatively rotated only about 45 degrees around the optical axis.
It should be noted that in the eighth aspect of the present invention, to relatively rotate a first negative lens and a second negative lens about 45 degrees around the optical axis means that the relative angle of the predetermined crystal axes (for example, crystal axes [010], [001], [01xe2x88x921], or [011]) which are facing in different directions from the optical axis in a first negative lens and a second negative lens is about 45 degrees around the optical axis. Furthermore, when the crystal axis [100] serves as the optical axis, rotational asymmetry stemming from the effect of birefringence with the optical axis at the center appears at a 90 degree period, so in the eighth aspect of the invention, to relatively rotate only about 45 degrees around the optical axis means the same as relatively rotating only about 45 degrees+(n*90 degrees) around the optical axis (where n is a whole number).
A ninth aspect of the present invention provides a projection optical system capable of forming a reduced image of a first surface at a second surface, wherein the projection optical system is arranged in the optical path between the pupil position of the second surface side and the second surface, has a substantially transmissive characteristic for light with a wavelength of 200 nm or less, and is provided with at least one radiation transmissive member formed such that the crystal axis [110] or an optically equivalent crystal axis to the crystal axis [110] nearly aligns with the optical axis.
A tenth aspect of the present invention provides a projection optical system capable of forming a reduced image of a first surface at a second surface, wherein at least one radiation transmissive member of the radiation transmissive members exceeding a maximum angle of the transmitting light ray of 20 degrees to the optical axis has substantially transmissive characteristics for light with a wavelength of 200 nm or less, and is formed such that the crystal axis [110] or an optically equivalent crystal axis to the crystal axis [110] nearly aligns with the optical axis.
An eleventh aspect of the present invention provides a projection optical system capable of forming a reduced image of a first surface at a second surface, wherein the projection optical system is provided with: a third group of transmissive members formed such that the crystal axis [100] or an optically equivalent crystal axis to the crystal axis [100] nearly aligns with the optical axis, and has substantially transmissive characteristics for light with a wavelength of 200 nm or less; a fourth group of transmissive members formed such that the crystal axis [100] or an optically equivalent crystal axis to the crystal axis [100] nearly aligns with the optical axis, and has substantially transmissive characteristics for light with a wavelength of 200 nm or less; wherein the third group of transmissive members and the fourth group of transmissive members have a positional relationship relatively rotated about 90 degrees around the optical axis; and both the third group of transmissive members and the fourth group of transmissive members are arranged in the optical path between the pupil position on the second surface side and the second surface.
A twelfth aspect of the present invention provides a projection optical system capable of forming a reduced image of a first surface at a second surface, wherein the projection optical system is provided with: a third group of radiation transmissive members formed such that the crystal axis [110] or an optically equivalent crystal axis to the crystal axis [110] nearly aligns with the optical axis, and has substantially transmissive characteristics for light with a wavelength of 200 nm or less; a fourth group of radiation transmissive members formed such that the crystal axis [110] or an optically equivalent crystal axis to the crystal axis [110] nearly aligns with the optical axis, and has substantially transmissive characteristics for light with a wavelength of 200 nm or less; wherein the third group of radiation transmissive members and the fourth group of radiation transmissive members have a positional relationship relatively rotated about 90 degrees around the optical axis; and in both the third group of radiation transmissive members and the fourth group of radiation transmissive members, the maximum angle of the transmitting light ray to the optical axis is greater than 20 degrees.
It should be noted that in the eleventh and twelfth aspects of the present invention, to relatively rotate the first group of lens elements and the second group of lens elements about 90 degrees around the optical axis means that the relative angle of the predetermined crystal axes (for example, crystal axes [001], [xe2x88x92111], [xe2x88x92110], or [1xe2x88x9211]) which are facing in different directions from the optical axis in the first group of lens elements and the second group of lens elements is about 90 degrees around the optical axis. Furthermore, when the crystal axis [110] serves as the optical axis, rotational asymmetry stemming from the effect of birefringence with the optical axis at the center appears at a 180 degree period, so in the eleventh and twelfth aspects of the invention, to relatively rotate only about 90 degrees around the optical axis means the same as relatively rotating only about 90 degrees+(n*180 degrees) around the optical axis (where n is a whole number).
According to preferred embodiments in the eleventh and twelfth aspects of the invention, at least one of the third group of radiation transmissive members and the fourth group of radiation transmissive members has at least one aspherical surface. Further, it is preferable that the conditional expression |T3xe2x88x92T4|/TA less than 0.025 is satisfied, wherein T3 is the total thickness (center thickness) of the third group of radiation transmissive members along the optical axis, T4 is the total thickness of the fourth group of radiation transmissive members along the optical axis, and TA is the total thickness along the optical axis of all the radiation transmissive members comprising the projection optical system. Furthermore, the third group of radiation transmissive members and the fourth group of radiation transmissive members are preferably formed as one optical member by optical contact or by adhesion.
A thirteenth aspect of the present invention provides a projection optical system which includes a plurality of lenses, a concave reflective mirror and a negative lens arranged in proximity to the concave reflective mirror, and which is capable of forming a reduced image of a first surface at a second surface, wherein the negative lens has substantially transmissive characteristics for light with a wavelength of 200 nm or less, and is formed such that the crystal axis [110] or an optically equivalent crystal axis to the crystal axis [110] nearly aligns with the optical axis.
A fourteenth aspect of the present invention provides a projection optical system including a plurality of lenses, a concave reflective mirror, and a first negative lens and a second negative lens arranged in proximity to the concave reflective mirror, and capable of forming a reduced image of a first surface at a second surface, wherein: the first negative lens is formed such that the crystal axis [110] or an optically equivalent crystal axis to the crystal axis [110] nearly aligns with the optical axis, and has substantially transmissive characteristics for light with a wavelength of 200 nm or less; the second negative lens is formed such that the crystal axis [110] or an optically equivalent crystal axis to the crystal axis [110] nearly aligns with the optical axis, and has substantially transmissive characteristics for light with a wavelength of 200 nm or less; and the first negative lens and second negative lens have a positional relationship relatively rotated about 90 degrees around the optical axis.
It should be noted that in the fourteenth aspect of the present invention, to relatively rotate the first negative lens and the second negative lens about 90 degrees around the optical axis means that the relative angle of the predetermined crystal axes (for example, crystal axes [001], [xe2x88x92111], [xe2x88x92110], or [1xe2x88x9211]) which are facing in different directions from the optical axis in the first group of lens elements and the second group of lens elements is about 90 degrees around the optical axis. Furthermore, when the crystal axis [110] serves as the optical axis, rotational asymmetry stemming from the effect of birefringence with the optical axis at the center appears at a 180 degree period, so in the fourteenth aspect of the invention, to relatively rotate only about 90 degrees around the optical axis means the same as relatively rotating only about 90 degrees+(n*180 degrees) around the optical axis (where n is a whole number).
A fifteenth aspect of the present invention provides a projection optical system capable of forming a reduced image of a first surface at a second surface, wherein the projection optical system is provided with: a fifth group of radiation transmissive members formed such that the crystal axis [111] or an optically equivalent crystal axis to the crystal axis [111] nearly aligns with the optical axis, and has substantially transmissive characteristics for light with a wavelength of 200 nm or less; a sixth group of radiation transmissive members formed such that the crystal axis [111] or an optically equivalent crystal axis to the crystal axis [111] nearly aligns with the optical axis, and has substantially transmissive characteristics for light with a wavelength of 200 nm or less; wherein the fifth group of radiation transmissive members and the sixth group of radiation transmissive members have a positional relationship relatively rotated about 60 degrees around the optical axis; and both the fifth group of radiation transmissive members and the sixth group of radiation transmissive members are arranged in the optical path between the pupil position on the second surface side and the second surface.
A sixteenth aspect of the present invention provides a projection optical system capable of forming a reduced image of a first surface at a second surface, wherein the projection optical system is provided with: a fifth group of radiation transmissive members formed such that the crystal axis [111] or an optically equivalent crystal axis to the crystal axis [111] nearly aligns with the optical axis, and has substantially transmissive characteristics for light with a wavelength of 200 nm or less; a sixth group of radiation transmissive members formed such that the crystal axis [111] or an optically equivalent crystal axis to the crystal axis [111] nearly aligns with the optical axis, and has substantially transmissive characteristics for light with a wavelength of 200 nm or less; wherein the fifth group of radiation transmissive members and the sixth group of radiation transmissive members have a positional relationship relatively rotated about 60 degrees around the optical axis; and in both the fifth group of radiation transmissive members and the sixth group of radiation transmissive members, the maximum angle of the transmitting light ray to the optical axis is greater than 20 degrees.
It should be noted that in the eleventh and twelfth aspects of the present invention, to relatively rotate the fifth group of radiation transmissive members and the sixth group of radiation transmissive members about 60 degrees around the optical axis means that the relative angle of the predetermined crystal axes (for example, crystal axes [xe2x88x92111], [11xe2x88x921], or [1xe2x88x9211]) which are facing in different directions from the optical axis in the fifth group of radiation transmissive members and the sixth group of radiation transmissive members is about 60 degrees around the optical axis. Furthermore, when the crystal axis [111] serves as the optical axis, rotational asymmetry stemming from the effect of birefringence with the optical axis at the center appears at a 120 degree period, so in the eleventh and twelfth aspects of the invention, to relatively rotate only about 60 degrees around the optical axis means the same as relatively rotating only about 60 degrees+(n*120 degrees) around the optical axis (where n is a whole number).
According to preferred embodiments of the fifteenth and sixteenth aspects of the invention, at least one of the fifth group of radiation transmissive members and the sixth group of radiation transmissive members has at least one aspherical surface. Further, it is preferable that the conditional expression |T5xe2x88x92T6|/TA less than 0.025 is satisfied, wherein T5 is the total thickness (center thickness) of the fifth group of radiation transmissive members along the optical axis, T6 is the total thickness of the sixth group of radiation transmissive members along the optical axis, and TA is the total thickness along the optical axis of all the radiation transmissive members comprising the projection optical system. Furthermore, the fifth group of radiation transmissive members and the sixth group of radiation transmissive members are preferably formed as one optical member by optical contact or by adhesion.
A seventeenth aspect of the present invention provides a projection optical system including a plurality of lenses, a concave reflective mirror, and a first negative lens and a second negative lens arranged in proximity to the concave reflective mirror, and capable of forming a reduced image of a first surface at a second surface, wherein: the first negative lens is formed such that the crystal axis [111] or an optically equivalent crystal axis to the crystal axis [111] nearly aligns with the optical axis, and has substantially transmissive characteristics for light with a wavelength of 200 nm or less; the second negative lens is formed such that the crystal axis [111] or an optically equivalent crystal axis to the crystal axis [111] nearly aligns with the optical axis, and has substantially transmissive characteristics for light with a wavelength of 200 nm or less; and the first negative lens and second negative lens have a positional relationship relatively rotated about 60 degrees around the optical axis.
It should be noted that in the seventeenth aspect of the present invention, to relatively rotate the first negative lens and the second negative lens about 60 degrees around the optical axis means that the relative angle of the predetermined crystal axes (for example, crystal axes [xe2x88x92111], [11xe2x88x921], or [1xe2x88x9211]) which are facing in different directions from the optical axis in the first group of lens elements and the second group of lens elements is about 60 degrees around the optical axis. Furthermore, when the crystal axis [111] serves as the optical axis, rotational asymmetry stemming from the effect of birefringence with the optical axis at the center appears at a 120 degree period, so in the seventeenth aspect of the invention, to relatively rotate only about 60 degrees around the optical axis means the same as relatively rotating only about 60 degrees+(n*120 degrees) around the optical axis (where n is a whole number).
An eighteenth aspect of the present invention provides a projection optical system capable of forming a reduced image of a first surface at a second surface, wherein the projection optical system: is provided with a radiation transmissive member formed of a crystal having substantially transmissive characteristics for light with a wavelength of 200 nm or less; and a crystal coat formed on the crystal is formed on the surface of the radiation transmissive member; and the crystal direction of the radiation transmissive member and the crystal direction of the crystal coat are different.
According to a preferred embodiment of the eighteenth aspect of the invention, the crystal direction along the optical axis of the radiation transmissive member and the crystal direction along the optical axis of the crystal coat are different. Alternatively, the crystal direction along the optical axis of the radiation transmissive member and the crystal direction along the optical axis of the crystal coat nearly the same, and the radiation transmissive member and the crystal coat preferably have a positional relationship relatively rotated a predetermined angle around the optical axis.
Here, a radiation transmissive member and a crystal coat having a positional relationship relatively rotated a predetermined angle around the optical axis means that the relative angle around the optical axis of specified crystal axes facing different directions from the optical axis in a radiation transmissive member and a crystal coat is a predetermined angle.
A nineteenth aspect of the present invention provides a projection optical system capable of forming a reduced image of a first surface at a second surface, wherein the projection optical system is provided with: a first group of radiation transmissive members formed such that the crystal axis [100] or an optically equivalent crystal axis to the crystal axis [100] nearly aligns with the optical axis, and has substantially transmissive characteristics for light with a wavelength of 200 nm or less; a third group of radiation transmissive members formed such that the crystal axis [110] or an optically equivalent crystal axis to the crystal axis [110] nearly aligns with the optical axis, and has substantially transmissive characteristics for light with a wavelength of 200 nm or less; and a fifth group of radiation transmissive members formed such that the crystal axis [111] or an optically equivalent crystal axis to the crystal axis [111] nearly aligns with the optical axis, and has substantially transmissive characteristics for light with a wavelength of 200 nm or less.
According to preferred embodiments of the invention, the projection optical system is used in an exposure apparatus that moves the first surface and the second surface along a scan direction to scan expose an image of the first surface onto the second surface, and a slit-shaped or arc-shaped exposure area does not intersect the optical axis of the projection optical system. The projection optical system preferably is provided with: a refractive type first optical imaging system to form a first intermediate image of the first surface; a second optical imaging system, having at least one negative lens and a concave reflective mirror, to form the first intermediate image into a second intermediate image of nearly the same magnification near the first intermediate image forming position, based on the light beam from the first intermediate image; a refractive type third optical imaging system to form a reduced image of the second intermediate image onto the second surface based on the light beam from the second intermediate image; a first optical path folding mirror arranged in the optical path between the first optical imaging system and the second optical imaging system; and a second optical path folding mirror arranged in the optical path between the second optical imaging system and the third optical imaging system.
It should be noted that in the above-described embodiments, the effective area of the first optical path folding mirror and the effective area of the second optical path folding mirror preferably have a reflective surface formed across the whole of the planar surface. It is preferable that the effective area of the first optical path folding mirror and the effective area of the second optical path folding mirror do not have a spatial overlap, and they are arranged such that the whole light beam from the first surface is guided to the second surface. Further, according to the above-described embodiments, all lenses comprising the first optical imaging system and the third optical imaging system are arranged along a single straight line of the optical axis. Furthermore, the projection optical system is preferably provided with a catadioptric type imaging system including a concave reflective mirror arranged in the optical path between the first surface and the second surface; a refractive type imaging system arranged in the optical path between the catadioptric type optical imaging system and the second surface; a first optical path folding mirror arranged in the optical path between the first surface and the catadioptric type optical imaging system; and a second optical path folding mirror placed in the optical path arranged in the optical path between the catadioptric type optical imaging system and the refractive type optical imaging system.
Another aspect of the present invention provides an exposure apparatus provided with: an illumination system to illuminate a mask serving as the first surface, and a projection optical system according to any of the above aspects to form a pattern image formed on the mask at a photosensitive substrate serving as the second surface.
Another aspect of the present invention provides an exposure method to illuminate a mask formed with a pattern, and to form an image of a pattern of the mask onto a photosensitive substrate via a projection optical system according to the invention.